My husband of the ever-active intellect (aka Hoosier Gadfly) pointed out something that was obvious once he came up with it -- but I've never heard it discussed before. If you want to make an exact genetic replica of someone, start with the same biochemical building blocks that that person started with, it isn't enough just to clone 'em. You need identical mitochondrial DNA. He suggested inserting the regular (I forget what to call it) DNA in an egg from the person's mother's female line.
That could make it more difficult to clone people who've been gone a while, even if their DNA is somehow preserved. I guess one has to plan ahead and preserve an appropriate egg as well. . . .